The present invention relates to the cooling and damping of rotor blades and stationary vanes (both of which are generically referred to herein as “blades” unless otherwise indicated). The invention relates more particularly to cooling and damping of blades using a coolant supplied to internal channels in the blades that are lined with a shape memory alloy, or superelastic alloy (both of which are hereinafter generally referred to as a “shape memory alloy”).
Compressors and turbines are examples of the turbo-machinery that include a number of rotor blades that are driven in a rotational sense by a gas passing therethrough. For example, a turbine produces rotational power by receiving high-temperature, high-pressure gases such as combustion gases from a fuel combustor, and expanding the gases to a lower temperature and lower pressure via an alternating series of stationary vanes and rotating blades. A gas turbine may have a single “stage” consisting of a row of stationary vanes followed by a row of rotor blades, or it may have two or more such stages in series.
In high-performance gas turbine engines, the temperature of the combustion gases entering the first stage of the turbine typically is so high that the available materials for constructing the stationary vanes and rotor blades are not capable of withstanding the extreme temperature without some type of active cooling of the blades and vanes. Thus, modern advances in gas turbine technology have largely been made through discoveries of improved materials capable of withstanding higher temperatures, coupled with improved cooling schemes. These cooling schemes have included film cooling techniques and the circulation of coolant through internal passages defined by a turbine blade as described in more detail by U.S. patent application Ser. No. 10/029,451 entitled Fluid-Cooled Turbine Blades by James Lobitz, et al. filed Dec. 19, 2001; the contents of which are incorporated herein in their entirety.
The blades of compressors, turbines and other turbo-machinery oftentimes also disadvantageously vibrate during operation. These vibrations are primarily due to disturbances in the working fluid and the relatively high rotational speeds at which these machines operate. Among other things, blade vibration may shorten the life and reduce the operating range, including the maximum rotational speed, of a compressor, turbine or other turbo-machinery. In order to improve the efficiency with which compressors, turbines and other turbo-machinery operate and to permit the rotational speeds of these turbo-machines to be further increased, it is desirable to reduce the vibration of the blades. As such, several techniques have been developed to at least partially damp blade vibration.
One device intended to reduce blade vibration applies friction at the tips of the blades. Unfortunately, these damping devices include a large number of components which increase the cost and complexity of the damping devices. In addition, these damping devices or components thereof may possibly become separated from the blades, thus creating the risk of foreign object damage to the blades and/or other portions of the compressor, turbine or other turbo-machinery incorporating these damping devices.
Another damping technique employs annular vibration, or shock, absorbers formed of shape memory alloys that are disposed proximate the base or root of the blade. Since the vibrations are generally more pronounced proximate the tips of the blades, however, the annular vibration, or shock, absorbers placed near the base or root of the blades may not damp the vibrations as efficiently as desired.
Accordingly, although various techniques have been developed to damp blade vibrations, it would be desirable to improve the damping of blade vibrations in order to increase the life and operating range, including rotational speeds, of turbines, compressors and other turbo-machinery.